It is a disorder caused by the removal of a small portion of chromosome 22. It occurs near the center of the chromosome in a place designated as q11.2.
DiGeorge syndrome encompasses the following disorders phenotypically, which is also known by several other names:
- Autosomal dominant Opitz G / BBB syndrome.
- Cardiofacial syndrome of Cayler.
- Face syndrome with conotruncal anomaly (CTAF).
- DiGeorge syndrome.
- Sedlackova syndrome.
- Shprintzen syndrome.
- Velo-cardio-facia syndrome.
These syndromes were described as separate entities based on their prominent characteristics and named as such before the discovery that they shared a common microdeletion of the critical region of DGS, on chromosome 22 in the DiGeorge syndrome band.
Because the signs and symptoms of DiGeorge syndrome are so varied, different groupings of characteristics were once described as separate conditions.
Doctors called these conditions the DiGeorge syndrome, the velocardiofacial syndrome (also called Shprintzen syndrome) and the syndrome syndrome conotruncal face.
In addition, some children with DiGeorge Syndrome were diagnosed with the autosomal dominant form of Opitz G / BBB syndrome and Cayler’s cardiofacial syndrome.
DiGeorge syndrome has many possible signs and symptoms that can affect almost any part of the body. The characteristics of this syndrome vary widely, even among affected members of the same family.
Common signs and symptoms include heart abnormalities that are often present from birth, an opening in the roof of the mouth (cleft palate), and distinctive facial features.
People with DiGeorge syndrome often experience recurrent infections caused by problems with the immune system, and some develop autoimmune disorders such as rheumatoid arthritis and Graves’ disease in which the immune system attacks the body’s own tissues and organs.
Affected individuals may also have breathing problems, kidney abnormalities, low blood calcium levels (which can lead to seizures), a decrease in blood platelets ( thrombocytopenia ), significant feeding difficulties, gastrointestinal problems, and hearing loss.
Skeletal differences are possible, including short stature and, less frequently, abnormalities of the bones of the spine.
Many children with DiGeorge syndrome have developmental delays, including delayed growth and development of speech, and learning problems. Later in life, they have a higher risk of developing mental illnesses such as schizophrenia, depression , anxietyand bipolar disorder .
In addition, affected children are more likely than children without DiGeorge syndrome to have attention deficit hyperactivity disorder (ADHD) and developmental conditions such as autism spectrum disorders that affect communication and social interaction.
Once the genetic basis for these disorders was identified, doctors determined that they were all part of a unique syndrome with many possible signs and symptoms. To avoid confusion, this condition is usually called DiGeorge syndrome, a description based on its underlying genetic cause.
DiGeorge syndrome affects approximately 1 in 4,000 people. However, the condition may actually be more common than this estimate because doctors and researchers suspect that it is underdiagnosed due to its variable characteristics.
The condition may not be identified in people with mild signs and symptoms, or may be confused with other disorders with overlapping characteristics.
Most people with DiGeorge syndrome lack a sequence of approximately 3 million building blocks of DNA (base pairs) on a copy of chromosome 22 in each cell.
This region contains 30 to 40 genes, many of which have not been well characterized. A small percentage of affected individuals have shorter deletions in the same region.
This condition is described as a contiguous gene deletion syndrome because it is the result of the loss of many genes that are very close together.
Researchers are working to identify all the genes that contribute to the characteristics of DiGeorge syndrome.
They have determined that the loss of a particular gene on chromosome 22, TBX1, is probably responsible for many of the characteristic signs of the syndrome (such as heart defects, cleft palate, distinctive facial features, hearing loss, and low calcium levels).
Some studies suggest that an elimination of this gene can also contribute to behavioral problems. The loss of another gene, COMT, in the same region of chromosome 22 may also help explain the increased risk of behavioral problems and mental illness.
The loss of additional genes in the removed region probably contributes to the various characteristics of DiGeorge syndrome.
The inheritance of DiGeorge syndrome is considered autosomal dominant because a deletion in a copy of chromosome 22 in each cell is sufficient to cause the condition. Most cases of DiGeorge syndrome are not inherited, however.
Elimination occurs more frequently as a random event during the formation of reproductive cells (ovules or sperm) or in early fetal development. In general, affected people do not have a history of the disorder in their family, although they can transmit the disease to their children.
In about 10 percent of cases, a person with this condition inherits the deletion on chromosome 22 of a parent. In inherited cases, other members of the family may also be affected.
Signs and symptoms
Patients with DiGeorge syndrome generally have predominant facial features. The most common include the following:
- Retrognathia or micrognathia.
- How to larga.
- High and wide nasal bridge.
- Narrow palpebral fissures.
- Small teeth.
- Mouth down.
- Philtrum (subnasal sulcus) short.
- Under adjustment, malformed ears.
- Dimple on the tip of the nose.
Congenital heart defects, cleft palate or soft palate incompetence and immune deficiencies are common. Patients may have short stature and occasional cases of growth hormone deficiency.
Kidney, lung, gastrointestinal (GI), skeletal, and ophthalmologic abnormalities may also occur.
Children and adults with DiGeorge syndrome have high rates of behavioral, psychiatric and communication disorders. In children, these include attention deficit / hyperactivity disorder, anxiety, autism, and affective disorders.
Adults have a high rate of psychotic disorders, particularly schizophrenia.
- Analysis of chromosomal microarrays (CMA) or comparative genomic matrix hybridization (aCGH)
- Fluorescent in situ hybridization (FISH).
- Studies of the TBX1 gene.
- Amplification of the probe dependent on multiplex ligature (MLPA).
Additional Laboratory Tests
- Complete blood cell count (CBC).
- Serum studies of calcium and parathyroid hormone (PTH).
T Cell and Function Count Evaluation.
- Flow cytometry.
- Polymerase chain reaction assay with reverse transcriptase (RT PCR) to evaluate the output of thymic cells for the detection of TCR excision circles (TREC).
- Studies of antibody response.
Imaging studies used in the diagnosis of thymic and cardiovascular abnormalities in 22q11.2DS include the following:
- Bone scan.
- Magnetic resonance (MRI).
- Computed tomography (CT).
- Angiography and magnetic resonance angiography (MRA)
Defecto Cardiac Congenital
If there is a heart murmur or other signs of a heart defect, consult a cardiologist immediately, especially in the neonatal period.
Start calcium supplementation after performing the appropriate tests (simultaneous serum calcium and serum PTH levels). Supplementation with vitamin D may be necessary.
Early transplantation (ie, before the onset of infections) can promote successful immune reconstitution for subjects with complete absence of thymus (1% of DiGeorge syndrome subjects).
A potential alternative treatment, the adoptive transfer of mature T cells (ATMTC) through bone marrow transplantation, has emerged as a successful therapy for DiGeorge syndrome.
For subjects with thymic hypoplasia, prophylactic antibiosis and antifungals are useful during the first year of life. The management of autoimmune complications is important for older subjects.
DiGeorge syndrome or DGS has a wide range of clinical features, which include the following:
- Facies anormal.
- Congenital heart defects.
- Hypoparathyroidism with hypocalcemia .
- Cognitive, behavioral and psychiatric problems.
- Greater susceptibility to infections due to aplasia or thymic hypoplasia.
Some refer collectively to these by the acronym CATCH-22 (cardiac defects, abnormal facies, thymic hypoplasia, cleft palate and hypocalcemia resulting from the deletion of DiGeorge syndrome).
DiGeorge syndrome was originally described as a developmental field defect in the third and fourth branchial pouches, which often occur in the neonatal period with hypocalcemia and severe immunodeficiency.
Later, conotruncal heart defects were included. The velocardiofacial syndrome, on the other hand, was initially recognized as a syndrome of palatal defects, conotruncal heart defects, and characteristic facial features.
DiGeorge syndrome partial vs DiGeorge syndrome complete, based on immunological characteristics
Hypoplasia or thymic aplasia that leads to defective T cell function is one of the main features of DiGeorge syndrome. Depending on the proliferative responses of T cells to mitogens, the immunological characteristics of DiGeorge syndrome can be classified as partial or complete.
Patients with partial DiGeorge syndrome have a proliferative response below normal to mitogens, and immune parameters may improve over time. Interleukin (IL) -7 may play a critical role in T cell homeostasis in patients with partial DiGeorge syndrome.
However, in subjects with thymic hypoplasia, despite the compensatory increase in the number of T cells, it is reported that the TCR repertoire is decreased compared to normal controls.
B Cell Defects
Although DiGeorge syndrome is classified as a T lymphocyte immunodeficiency, B lymphocyte defects also occur.
A review of 1023 patients with DiGeorge syndrome revealed that 6% of patients older than 3 years had hypogammaglobulinemia and that 3% of patients with DiGeorge syndrome were receiving immunoglobulin replacement therapy .
The prognosis for DiGeorge syndrome varies widely, depending largely on the nature and degree of involvement of different organs, and it is important to note that many adults live long and productive lives.
The most common cause of mortality in DiGeorge syndrome is a congenital heart defect and the second most common is severe immune deficiency.
Mortality is higher in childhood due to the severity of these 2 conditions. Babies with thymic aplasia present with severe immunodeficiency and typically die from sepsis , caused by bacterial or fungal infections.